1. Field of the Invention
The present invention relates to a transmission assembly for a bicycle for leisure purpose, and more particularly to a transmission assembly for a bicycle having forward/back gear operated by a pair of reciprocating pedals.
2. Description of the Related Art
Taiwan Utility Model Publication No. 333178 issued on Jun. 1, 1998 and entitled xe2x80x9cTRANSMISSION IMPROVEMENT FOR BICYCLESxe2x80x9d discloses a bicycle frame having a guard plate mounted to each of two ends of a front chain wheel shaft. A shaft block is inserted into a central axle hole of each guard plate and is fixed to the front chain wheel shaft by a pin. A semi-circular weight is screwed into one of the guard plates and includes a seat embedded in an offset position. The seat is screwed into the weight by a tri-claw like fixing frame. A pedal mechanism consisting of a link and a pedal is securely mounted in the seat. Thus, the pedal mechanism is provided in an offset manner. In addition, a second pedal mechanism is provided to the other guard plate. The two pedal mechanisms are arranged to have a phase difference of 180xc2x0. By means of arrangement of the weights and the offset pedal mechanisms, inertial motions and gravitational accelerating motions are provided. Nevertheless, the pedals must be rotated to empower the pedal mechanisms, and this requires the cyclist to make larger movements. Smaller movements of the cyclist are required for rearward movement of the bicycle and the empowerment to the pedal mechanisms by means of rotating the pedals does not fit. Larger movements of the cyclist for rotating the pedals do not allow the cyclist to turn around easily for viewing the situation behind him/her and might be unable to control the rearward movement of the bicycle.
It is the primary object of the present invention to provide a bicycle with reciprocating pedals for providing forward/back gear such that the cyclist may turn around to see the situation behind him/her. Thus, the bicycle can be moved backward under a safer condition to thereby provide leisure and sporting effects.
In accordance with the present invention, a bicycle transmission assembly comprises a gear shifting device and a reciprocating pedal device that are mounted to a bicycle frame. The reciprocating pedal device comprises a reverse gear train consisting of a first reverse gear and a second reverse gear that are meshed with each other. Each reverse gear is connected via a torque rod and a link to a mediate portion of an associated pedal rod. The reverse gears rotate in reverse directions so as to make the pedal rods move horizontally and reciprocatingly. Swaying movements of the pedal rods drive a single direction gear mechanism to make a single direction gear of the single direction gear mechanism rotate in only one direction.
The gear shifting device comprises a first idler gear and a second idler gear that are meshed with each other and both carried by a carrier member. A follower gear and the first idler gear are coaxially mounted with each other. The follower gear is connected to the single direction gear of the reciprocating pedal device via a transmission element. The carrier member includes a shaft that is rotatably supported by the bicycle frame. The carrier member is connected to a gear shifting lever via an arm and a link. Pivotal movements of the gear shifting lever cause rotational movements of the carrier member such that the first idler gear and the second idler gear are turned about the axis of the shaft of the carrier until the first idler gear or the second idler gear is meshed with a transmission gear to thereby drive the wheels of the bicycle. Selective engagement of the transmission gear with the first idler gear or the second idler gear upon manual operation of the gear shifting lever controls the rotating direction of the transmission gear, thereby controlling forward or rearward rotations of the wheels of the bicycle.
Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.